<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            margin: 0;
            height: 100vh;
            background: #000;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .container {
            width: 50px;
            height: 300px;
            border: 1px solid #fff;
            border-radius: 5px;
        }

        .item {
            width: 100%;
            height: 100%;
            background: repeating-linear-gradient(45deg, #eee 0px, #eee 20px, #3158c4 20px, #3158c4 40px);
            background-size: 50px 56px;
            animation: move 1s infinite linear;
        }

        @keyframes move {
            to {
                background-position: 0 56px;
            }
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="item"></div>
    </div>
</body>

</html>